Linux_DHCP中继服务配置

一、DHCP中继代理
（1）在服务器上建立多个网段的作用域
 

[root@localhost ~]# cat /etc/dhcpd.conf
ddns-update-style interim;
ignore client-updates;
        option subnet-mask              255.255.255.0;
        option domain-name-servers      202.106.0.20,202.106.148.1;
        option time-offset              -18000; # Eastern Standard Time
        default-lease-time 21600;
        max-lease-time 43200;
subnet 192.168.2.0 netmask 255.255.255.0 {
        option routers                  192.168.2.1;
        range dynamic-bootp 192.168.2.128 192.168.2.254;
}
subnet 192.168.3.0 netmask 255.255.255.0 {
        option routers                  192.168.3.1;
        range dynamic-bootp 192.168.3.128 192.168.3.254;
}
subnet 192.168.4.0 netmask 255.255.255.0 {
        option routers                  192.168.4.1;
        range dynamic-bootp 192.168.4.128 192.168.4.254;
}

（2）开启中继代理服务器的路由转发功能
/etc/sysctl.conf net.ipv4.ip_forward=1 sysctl –p
 

[root@localhost ~]# cat /etc/sysctl.conf
# Kernel sysctl configuration file for Red Hat Linux
#
# For binary values, 0 is disabled, 1 is enabled.  See sysctl(8) and
# sysctl.conf(5) for more details.

# Controls IP packet forwarding
net.ipv4.ip_forward = 1

# Controls source route verification
net.ipv4.conf.default.rp_filter = 1

# Do not accept source routing
net.ipv4.conf.default.accept_source_route = 0

# Controls the System Request debugging functionality of the kernel
kernel.sysrq = 0

# Controls whether core dumps will append the PID to the core filename
# Useful for debugging multi-threaded applications
kernel.core_uses_pid = 1

# Controls the use of TCP syncookies
net.ipv4.tcp_syncookies = 1

# Controls the maximum size of a message, in bytes
kernel.msgmnb = 65536

# Controls the default maxmimum size of a mesage queue
kernel.msgmax = 65536

# Controls the maximum shared segment size, in bytes
kernel.shmmax = 4294967295

# Controls the maximum number of shared memory segments, in pages
kernel.shmall = 268435456
[root@localhost ~]# sysctl -p
net.ipv4.ip_forward = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
net.ipv4.tcp_syncookies = 1
kernel.msgmnb = 65536
kernel.msgmax = 65536
kernel.shmmax = 4294967295
kernel.shmall = 268435456

（3）改配置文件
/etc/sysconfig/dhcrelay INTER>接口名 接口名” DHCPSERVERS=服务器IP

 

[root@localhost ~]# cat /etc/sysconfig/dhcrelay
# Command line options here
INTERFACES="eth0 eth1 eth2"
DHCPSERVERS="192.168.2.2"

（4）启动服务
service dhcrelay start
（5）设置下次开机自动启动
chkconfig dhcrelay on
ps:对于使用虚拟机来做DHCP中继代理实验，最后需要一条指令“dhcrelay DHCP服务器的IP地址”，真实环境此步骤可以省略。